A diabetic woman has an AFP level of 2.3 MoM - why does αlpha say her AFP is raised, when my cut-off is 2.5 MoM?

AFP levels are, on average, lower in women with insulin-dependent diabetes (IDDM) than in non-diabetic women. The reduction is about 23% if AFP MoM values are not adjusted for maternal weight, and about 12% if the MoMs are weight-adjusted (this is because women with IDDM are, on average, heavier than other women, and part of the reduction in their AFP levels will be due to increased blood volume associated with their greater weight).

To account for the reduced levels, αlpha divides the AFP MoM in a diabetic woman by the appropriate correction factor (0.77 without weight adjustment, or 0.88 with weight adjustment), and compares the adjusted MoM with the cut-off. In this example, the adjusted MoM would be 2.3/0.77 = 2.98 MoM without adjustment for weight, or 2.3/0.88 = 2.61 MoM with adjustment for weight, both of which are higher than the cut-off of 2.5 MoM.

The unadjusted MoM is printed on the report.